Extreme Networks ExtremeWare 7.7, Command Reference Manual

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2528 ExtremeWare 7.7 Command Reference Guide
MPLS Commands—BlackDiamond Switch Only
configure mpls propagate-ip-ttl
configure mpls propagate-ip-ttl [enabled | disabled]
Description
Enables or disables the propagation of the IP time-to-live (TTL) field for routed IP packets. When
propagation is enabled, each LSR is viewed as a router hop from an IP TTL perspective. When
propagation is disabled, the LSP is viewed as a point-to-point link between the ingress LSR and the
egress LSR.
Syntax Description
This command has no arguments or variables.
Default
N/A
Usage Guidelines
This command enables and disables the propagation of the IP TTL value for routed IP packets. The
default setting is enabled.
NOTE
You must maintain identical
propagate-ip-ttl
settings on all LERs in the MPLS domain. Not doing so
may cause packets to loop endlessly and not be purged from the network if a routing loop is
inadvertently introduced.
When
propagate-ip-ttl
is disabled, the LSP is viewed as a point-to-point link between the ingress
LSR and the egress LSR. Intermediate LSRs in the MPLS network are not viewed as router hops (from
an IP TTL perspective). In this case, the IP TTL is decremented once by the ingress LSR and once by the
egress LSR. When disabled, the MPLS TTL is set to 255 by the ingress LSR and is independent of the IP
TTL.
When
propagate-ip-ttl
is enabled, each LSR is viewed as a router hop (from an IP TTL perspective).
When a packet traverses an LSP, it emerges with the same TTL value that it would have had if it had
traversed the same sequence of routers without being label-switched. When enabled, the MPLS TTL
field is initially set to the IP TTL field at the ingress LSR, and the IP TTL field is set to the MPLS TTL by
the egress LSR.
Example
The following command enables the propagation of the IP time-to-live (TTL) field for routed IP packets:
configure mpls propagate-ip-ttl enabled
History
This command was first available in an ExtremeWare IP Technology Services Release based on
v6.1.8b12.